auth_time id_token claim changed to float64

[narg95]

Describe the bug

PR #595 introduced a breaking change on auth_time claim data type in id_token. Previously the auth_time claim was of type int64 but this change transformed it to float64. Although values are still equivalent hydra tests expects an integer.

Test: TestAuthCodeWithDefaultStrategy/case=ensure_consistent_claims_returned_for_userinfo expects the auth_time

To Reproduce

1. Checkout hydra's integration with fosite v0.40 branch from PR #2526
2. Run

$ go test -failfast -v -short -tags sqlite -run TestAuthCodeWithDefaultStrategy/case=ensure_consistent_claims_returned_for_userinfo ./oauth2

Expected behavior

Test PASS